This invention relates generally to computer power supplies and is particularly directed to an arrangement for sequentially energizing and de-energizing various peripherals in a computer system in a controlled, predetermined manner.
Electronic systems frequently include a controller and a plurality of controlled devices coupled thereto. The controller typically provides commands to the controlled devices which, in turn, perform specific functions and provide requested data back to the controller for processing therein. One example of such an arrangement is found in the typical computer controlled terminal wherein a central processor unit (CPU) receives user initiated inputs such as from a keyboard and provides various control outputs to peripheral devices in the system. These peripherals may include the keyboard itself, a video display, a printer, a plotter, a modem and perhaps a disc memory.
In the prior art, these various peripherals have typically been energized during power up simultaneously at the start of computer terminal operation. However, each of these peripherals exhibits a unique, individual level of sensitivity or susceptibility to variations in the input power applied thereto. Thus, input voltage transients affect each of the aforementioned peripherals in a different manner in accordance with their respective operating characteristics. For example, because a disc memory device is more sensitive to input voltage variations than a printer, an AC line voltage variation may alter or completely erase data stored in the disc memory, or may even result in damage thereto, while having little or no affect on printer operation.
Input voltage transients are most frequently encountered when power is initially applied to or removed from the peripheral device. This variation is the result of AC line characteristics as well as voltage regulation limitations in the device itself. In addition, when several devices are connected in a common circuit and are powered up or turned on in a near simultaneous manner, the load variations imposed on the AC line frequently result in variations in the input voltage. These input voltage variations may not only prevent normal system operation, but may even damage various of the peripheral devices therein.
The present invention addresses the aforementioned problems encountered in the prior art in providing a computer power controller which sequentially and in a predetermined manner applies input power to and removes input power from a plurality of peripherals in a computer controlled system during system power up and power down. The sequence in which the supply voltage is applied to and removed from the various peripheral devices is determined by their relative sensitivity to input voltage and switching transients.